Airplane propeller



July 7, 1931. c, GUNN' I 1,813,877

AIRPLANE PROPELLER Fil-ed Aug. 16, 1927 Patented July 7, 1931 uu-lraogsraras" PATENT OFFICE W 1;. cm, or can ramcrsco. canmomnn, nssronon moamcnar'r era- 'cmmms comm, or am m'rno, CALIFORNIA, a. conrom'non AIRPLANE PBOPELL'EB Application filed August 18. 1927. Serial 11o. 21 3380.

This invention relates to improvements in the construction. of airplane propellers. The present form of propeller in common use has certain great disadvanta es. Due to the construction which in this orm is necessary to provide the requisite-strength, the blades are quite thick at andrfor some distance from the hub, so that this portion of the blades merely presses against and churns the air instead of cutting t rough the same in a useful manner.; At the same time, the blades are thin at their outer ends, and vibrate considerably when in rapid motion. Another disadvam tageous feature due to the use of the present propeller, which has nothing to do with the above objectionable point, is that at ordinary flying s eeds airplanes have a tendency to slip or s 'd in the air, owing to the fact that the ropeller does not have suflicient grip on, or rictional contact with, the air at the ri ht place, to enable the airplane to maintam a true course. It is true that this slippage is minimized and hardly noticeable at extremely high speeds, but such speeds cannot be maintained in every day use, and are of course detrimental to the life of the engine and plane.

The principal objects of my invention therefore are to provide an airplane propeller so constructed that it is useful in creating propellin power from the hub to the outer ends of t e blades; the latter maybe made of metal and may be ver light without any vibration, or distortion eveloping; the efiiciency of the blades is such that greater power and propulsive effort is developed with less power than is now required, and the operation of the (propeller automatically causes the usual skid ng and slippage to be eliminated without a high propeller speed being necessary, and the movement of t e airplane is steadied.

- A further object of the invention is .to produce a simple and inexpensive dev1ce and yet one which will be exceedingly effective for the purposefor which it is'designed.

Theseob'jects I accomplish b'y jmeans of I such structure and relative arrangement of arts as will fully appear by a perusal of the allowing specification and claims.

tween said armsto brace and strengthening In the drawings similar characters of ref erence indlcate corresponding parts in the several views:

Fig. '1 is a perspective elevation of my improved airplane propeller.

Fig.2 is a cross section of the same on the line 2-2 of Fig. 1. b Fig. 3 is a front elevation of the hub mem';

er. Y Fig. 4 is a top plan view of the same.

Fig. 5 is a cross section of, the propeller showing a method ofenabling the pitch of the blades to be altered.

Referring to the numerals of reference on the drawings, the hub member to which the blades are attached comprises a central and preferably cylindrical member 1,- taperbored as at 2 to receive the enginecrankshaft.

' Projecting radially and oppositely from and formed with the central member are arms 3 and arranged in pairs with their osed faces parallel to each other, as shown ig. 4. The faces of the arms 8 are set at a certain angle to the hub-axis but in the 0pposite direction. Also, the leading edges, of the rear arms are disposed somewhat ahead of the leading :edges'of the forward arms, with respect to the direction of rotation of I the propeller, as clearly shown in Fig. 3. I

Projectin 'outwardly from and longitudinally aline with the various arms are the blades 5. The blades are secured to the .opposed outer faces of the arms by bolts 6 with suitable spacers 7, about the bolts and be-.

the same without creating undue wind-resistance.

The blades adjacent their outer ends are connected by a bolt 8 with a spacer between the blades. F The blades are of rectangular form andprefe'rably made of sheet metal of a suitable gage, and are (if the same thickness throughout. They are, centrally positioned as to height on the hub-arms, so consequently the blades are disposed in ofiset planes with their leading edges in the same relation to each other as are those of the hubarms, as described above. Theblades along their leading edges are bent forwardly ate 1 slight angle, as at 10, while their following edges are bent back, as shown at 11.

In operation, it will be seen that the blades, which ma extend very close to the central 5 hub inem er, function with the same efficiency from end to end. Being very thin, they do notpress on but cut cleanly through the air at all points, and the hub arms are kept as thin as possible so that they offer a minimum of resistance to the air.

The forward blades, bearing directly, against the air, do most of the actual propelling work, the mainfunction of the rear blades being for steadying purposes although they also have a certain propulsive effectiveness which is increased by said blades being disposed somewhat ahead of the others in the direction of rotation of the propeller. The front blades, aided by the bent fins 10 and 11, have a tendency to pile up and compress the air in the space between the blades, and this compressed air exerts a steadying effect on the airplane, preventing the same from any tendency to slippage or skidding.

The fins also strengthen the blades preventing longitudinal deflection and transverse warping thereof and enabling the blades to be made very thin and light. Vibration of the blades at their outer ends is partly prevented by said fins, and partly by reason of the connecting bolts and spacers.

In the arrangement shown in Fig. 5, the hub and arm members are the same, but I employ removable wedge-shims 12 between the adjacent faces of the blades and hub arms, so that the pitch of the blades relative to the axis of the hub may be easily changed if necessary without altering the 0 design of the hub. Y

WhileI have shown but four blades, in practice it may be-possible to extend the structure to include six or eight-blades and thus increase the efficiency of the propeller.

5 Each blade would be braced to its adjacent blade, hence this multiplication of parts could be resorted to without sacrifice of strength.

From the foregoing description it will be readily seen that I have produced such a 0 device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the pigjesent and preferred construction of the device,'st ill in practice such devia 5 tions from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention what 0 I claim as new and useful and desire to secure by Letters Patent is:

1. An airplane propeller including a hub, pairs of rigid parallel-edged arms projecting radially from opposite sides of the hub,

5 and straight edged thin blades abutted against and secured to the arms, the major area of the blades .being straight in cross section and the width of the arms being equal to the width of such major area of the blades.

2. An airplane propeller including a hub, pairs of parallel rigid arms projectin radially from opposite sides of thehub, lades engaging the opposite faces of the corresponding arms from end to end of the same, and bolts common to both blades of a pair securing the same to the arms.

3. An airplane propeller including a hub, pairs of parallel rigid arms projecting radially from opposite sides of the hub, blades engaging the opposite faces of the corresponding arms from end to end of the same, bolts in pairs common to both .blades of a pair securing the same to the arms, and a spacer about each pair of bolts extending between the arms to enclose such bolts and brace the arms.

In testimony whereof I affix my signature.-

CHARLES H. GUNN. 

